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Calibrating Infrared Thermometers

The procedure for calibrating infrared thermometers, also called pyrometers, differs fundamentally from the procedure for other temperature sensors. In contrast to conventional thermometers, infrared thermometers measure not by contact with a medium but rather by evaluating the radiant heat given off by an object.

These pyrometers require a special calibration method, which we can implement in our temperature calibrators. We use a special calibration insert patented by SIKA.

To achieve optimum calibration results with infrared thermometers, we need to use a “black body” that is as close to ideal as possible. A black body is an idealised physical body which absorbs all incident (interfering) radiation while simultaneously radiating heat.

Such an idealised body would have a theoretical emission factor of 1. In practice, however, a body with an efficiency of 100% cannot be realised. With our patented infrared calibration insert, we can achieve an emission factor of 0.9994 – very close to the limits of what is physically possible.

The special feature of this insert is that the calibration surface at which the pyrometer is directed is located deep in the calibrator block. This makes it impervious to air flows which would otherwise influence the thermal radiation of the calibration surface. In addition, the calibration insert has an asymmetrical interior geometry, which prevents interfering radiation from penetrating to the base of the calibration insert, i.e. up to the calibration surface.

As with conventional thermometers, a comparison calibration between the calibrator and pyrometer is then carried out using the set temperature at the calibration surface.